ATE refers to an automated, usually computer-driven, approach to testing devices, such as semiconductors, electronic circuits, and printed circuit board assemblies. A device tested by ATE is referred to as a device under test (DUT).
ATE typically includes interleaved A2D converters, which are used to convert analog signals to digital format. Interleaving is a technique for increasing the bandwidth and sampling frequency of A2D converters. For example, two A2D converters may be used to sample the same signal at different times, and to produce two digital signals as a result. These digital signals may be used to produce an output signal that has an effective sampling frequency that is two times the sampling frequency of each individual A2D converter.
However, problems can result from interleaving. In particular, mismatches between analog and digital channels of the interleaved A2D converters can result in dynamic range degradation. In a fast Fourier transform (FFT) plot, this degradation shows up as spurious frequency components, or “spurs”. Two types of spurs can occur.
Image spurs are a result of gain and phase mismatches between analog and digital channels of interleaved A2D converters. Gain and phase errors produce error functions that are orthogonal to one another and that contribute to image spur energy at a particular frequency. Offset spurs are a result of offset differences between analog and digital channels of interleaved A2D converters. For a given offset mismatch, offset spurs are always at a same level. Offset spurs have a direct impact on spurious-free dynamic range (SFDR), and thus degrade a receiver's sensitivity.